public class BookShelf implements Aggregate{
	private Book[]  books;
	private int last = 0;
	public BookShelf (int maxsize){
		this.books = new Book[maxsize];
	}
	public Book getBookAt(int index){
		return books[index];
	}
	public void appendBook(Book book){
		this.books[last] = book;
		last++;
	}
	public int getLength() {
		return last;
	}
	public Iterator iterator (){
		return new BookShelfIterator(this);
	}
}
